A provider of data communications services typically provides a customer access to a large data communication network. This access is provided at “edge equipment” that connects a customer network to the large data communication network. As such, service providers have a broad range of customers with a broad range of needs, the service providers prefer to charge for their services in a manner consistent with which the services are being used. Such an arrangement also benefits the customer. To this end, a Service Level Agreement (SLA) is typically negotiated between customer and service provider. An SLA is a contract between the customer and service provider specifying agreed-to service level commitments. A Service Level Specification is a technical specification of the service being offered by the service provider to the customer.
To provide predetermined levels of service to a given customer, a service provider may consider monitoring and controlling the traffic from the given customer. Such monitoring and controlling is often referred to as “traffic management”.
Traditionally, Ethernet networks have had no traffic management capabilities. The Ethernet standard, known as IEEE 802.3, specifies the use of a PAUSE frame that allows a client to request a pause in transmission from a terminal attached to a given port. However, the PAUSE frame may only be employed on per port basis and may only be employed with respect to directly attached devices, which are not necessarily the originators of the traffic requiring management.
Recently, the Institute of Electrical and Electronics Engineers (IEEE) has introduced a user priority indication capability that enables the definition of up to eight service classes, also known as Classes of Service (CoS). A set of Ethernet frames that have the same user priority indication may receive the same level of performance within the service provider's network, where level of performance is usually measured in terms of frame loss ratio, frame delay and frame delay variation.
A standard known as IEEE 802.1Q defines an architecture for a general purpose Virtual Local Area Network (VLAN) that may be implemented within a customer network and describes a four-byte extension to Ethernet service frame headers known as an IEEE 802.1Q tag. This tag includes a number of fields, including a 12-bit VLAN-ID field and a three-bit “user priority” field used to signal compliant devices. These three bits (normally referred to as the “p-bits”) provide for eight possible values, which match those used in the known IEEE 802.1p user priority field. The p-bits and VLAN-ID may be used in an IEEE 802.1Q tag to provide an identity of a CoS and, therefore, may be said to represent a VLAN CoS ID.
To allow the deployment of Ethernet to carrier networks, the Metro Ethernet Forum (MEF) has recently been active in specifying traffic management capabilities for a metro Ethernet network (MEN). See MEF Technical Specification “Ethernet Service Model, Phase 1” available from www.metroethernetforum.org and hereby incorporated herein by reference. The work includes specifying Ethernet traffic parameters and traffic conditioning (policing) algorithms and actions. The MEF traffic parameters include: committed information rate (CIR), excess information rate (EIR), committed burst size (CBS), excess burst size (EBS). The traffic conditioning algorithms and actions relate to how Ethernet service frames are handled when they are found to comply with the traffic measurement parameters and when they are found not to comply with the traffic measurement parameters.
A single Ethernet VLAN has a capability to support the transmission of Ethernet service frames requiring different classes of service (up to eight). This capability differentiates Ethernet VLANs from connections defined by other technologies such as Frame Relay (FR) or Asynchronous Transfer Mode (ATM).
The MEF has defined basic traffic management at the User-Network Interface (UNI). The UNI may be defined as the physical demarcation point between the responsibility of a service provider and the responsibility of a subscriber. The service provider may provide one or more connections, each known as an Ethernet Virtual Connection (EVC), through the MEN. An EVC may be considered an instance of an association of two or more UNIs. Notably, it is known that a given UNI can support more than one EVC through the use of a Service Multiplexing capability.
As specified in “Ethernet Service Model, Phase 1” an Ethernet service frame is defined as any Ethernet frame transmitted across a UNI.
As provided for by an MEF definition of traffic management over a point-to-point EVC, provider edge equipment (PE) in a MEN receives, over a first UNI, an Ethernet service frame from customer edge equipment (CE) in a customer network. The provider and customer edge equipment may be switches, routers, switch/routers, or similar devices performing Ethernet transport/switching functions. The PE then identifies the EVC to which the service frame belongs (i.e., the PE determines an “EVC-ID”) and sends the service frame to the PE in the MEN that is connected to a customer network via a second UNI, which is associated with the first UNI in the EVC. Identification of the EVC is defined as involving determining a VLAN identifier (VLAN-ID) from the IEEE 802.1Q tag on the service frame. A map may then be consulted to determine the identity of an EVC corresponding to the determined VLAN-ID. The sending of the Ethernet service frame to the PE connected to the UNI that is associated with the first UNI in the EVC may be accomplished in many ways, as the MEN may be implemented using a protocol of the choice of the provider. Popular choices for MEN protocol include Ethernet, ATM, Multi-Protocol Label Switching (MPLS), FR, Internet Protocol (IP) and Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH).
To further coordinate MEF traffic management, the MEF has defined a term “Class of Service Identifier”, or CoS-ID, for information derivable from an Ethernet service frame that allows the identification of a required Class of Service treatment of the Ethernet service frame. Continuing the example presented hereinbefore, the MEF has described the derivation of the CoS-ID from the EVC-ID alone or from the EVC-ID in combination with the p-bits from the user priority field of the IEEE 802.1Q tag.
The MEF recommends determining a CoS to associate with a received Ethernet service frame based, at least in part, on the VLAN CoS-ID. In particular, the VLAN CoS-ID may be used to determine CoS aspects such as a Bandwidth Profile and forwarding treatment. A Bandwidth Profile may used to specify the traffic measurement parameters (e.g., CIR, CBS, EIR, EBS) that may be used for traffic policing and resource reservation.
In reviewing the MEF definitions, it may be considered that, although the basic traffic management techniques are useful, several enhancements may be implemented to improve the experience of both the customer and the provider.